add glistix-specifics release steps

RELEASE.md

@@ -1,5 +1,25 @@
 # Release checklist
 
+## Glistix checklist
+
+Additional instructions for Glistix:
+
+1. Follow "Gleam checklist" below.
+2. Ensure `compiler-core/src/version.rs` reports the correct Gleam version we're tracking.
+3. Bump Glistix version in each `Cargo.toml` (as well as `Cargo.lock` by running `cargo check` once), in the new project flake template at `compiler-cli/src/new.rs` and in `nix/glistix.nix`, as well as in `README.md`.
+4. Update the `cargoHash` in `nix/glistix.nix` by setting it to `""` and trying to build. The error will inform the new hash.
+5. Add changelog to the Glistix book (initially with "(Unreleased)" as the release date).
+6. Update the book as needed (there are several compiler internals documented there, including which patches we applied on top of the base Gleam compiler).
+7. Update the Glistix version in the book's installation instructions in "Getting Started".
+
+After release:
+
+1. Update the new version's changelog in the book to display the release date in UTC (both in the changelog's page and in the `src/SUMMARY.md`).
+2. Push a book tag with the new release version.
+3. Update Glistix library forks' flakes to point to the new Glistix version.
+
+## Gleam checklist
+
 1. Update the version in each `Cargo.toml`.
 2. Update versions in `src/new.rs` for stdlib etc if required.
 3. Run `make test build`.